Re: [PATCH v2 1/1] selinux: Transition to pasta_t in containers

[Max Chernoff <git@maxchernoff.ca>]

Hi Stefano

On Fri, 2025-05-16 at 18:11 +0200, Stefano Brivio wrote:
> Max, could it be that you're running stuff with some customised SELinux
> policy? By the way, with "unconfined disabled":

Simpler than that: I was testing something with SELinux permissive, and
I forgot to reenable it. Whoops. I'm getting the same results as you
now.

> Running with SELinux in permissive mode, I'm getting:
>
> # cat /var/log/audit/audit.log
> type=AVC msg=audit(1747410763.621:130615): avc:  denied  { search } for  pid=1352409 comm="pasta.avx2" name="1352408" dev="proc" ino=7022238 scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:container_runtime_t:s0-s0:c0.c1023 tclass=dir permissive=1
> type=AVC msg=audit(1747410763.621:130616): avc:  denied  { read } for  pid=1352409 comm="pasta.avx2" name="net" dev="proc" ino=7022285 scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:container_runtime_t:s0-s0:c0.c1023 tclass=lnk_file permissive=1
> type=AVC msg=audit(1747410763.622:130617): avc:  denied  { read } for  pid=1352409 comm="pasta.avx2" scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:container_runtime_t:s0-s0:c0.c1023 tclass=file permissive=1
> type=AVC msg=audit(1747410763.622:130618): avc:  denied  { read } for  pid=1352409 comm="pasta.avx2" name="ns" dev="proc" ino=7022284 scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:container_runtime_t:s0-s0:c0.c1023 tclass=dir permissive=1
> type=AVC msg=audit(1747410763.622:130619): avc:  denied  { open } for  pid=1352409 comm="pasta.avx2" path="/proc/1352408/ns" dev="proc" ino=7022284 scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:container_runtime_t:s0-s0:c0.c1023 tclass=dir permissive=1
> type=AVC msg=audit(1747410764.622:130620): avc:  denied  { read } for  pid=1352417 comm="pasta.avx2" name="net" dev="proc" ino=7022285 scontext=unconfined_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=system_u:system_r:container_t:s0:c609,c838 tclass=lnk_file permissive=1
>
> and:
>
> # audit2allow  -a
>
>
> #============= pasta_t ==============
> allow pasta_t container_runtime_t:dir { open read search };
> allow pasta_t container_runtime_t:file read;
> allow pasta_t container_runtime_t:lnk_file read;
> allow pasta_t container_t:lnk_file read;
>
> If I add those rules, everything works

Yes, adding those rules also fixes things for me.

> To me those denials look reasonable, in the sense that I would expect
> the namespace links to have container_runtime_t type.

I'm a little surprised that "container_runtime_t:file read" is necessary
since I thought that "container_runtime_t:lnk_file read" would be
sufficient to get the target of the link, but it indeed does not work
without it.

> (well, I'm not saying that's the solution...).

I guess the options are:

1. Add the above rules to the pasta SELinux policy

2. Have Podman change the context of /proc/self/ns/net to pasta_t

3. Have Podman pass a file descriptor to the netns instead of the path
   to the netns.

(1) is arguably the least secure, but is probably fine in practice?

> Max, could it be that you're running stuff with some customised SELinux
> policy? By the way, with "unconfined disabled":
>
>   https://bugzilla.redhat.com/show_bug.cgi?id=2330512
>
> we seem to have unconfined_t as type for those links:
>
> type=AVC msg=audit(1733378482.320:31258): avc:  denied  { open } for  pid=651955 comm="pasta.avx2" path="/proc/651954/ns" dev="proc" ino=2904841 scontext=staff_u:unconfined_r:pasta_t:s0-s0:c0.c1023 tcontext=staff_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=dir permissive=1
>
> ...but I'm not sure at which point in time exactly.

Ah, I wonder if that might be related to this:

    https://github.com/containers/buildah/issues/6160

But with the workaround documented there, and the rules from above,
"podman build" works as expected with the unconfined module disabled.

> Wait a moment. I don't think something SELinux-specific belongs to
> pasta's man page, because that's not relevant for all users and
> distributions.
>
> We could maintain that as an addition for Fedora and perhaps Gentoo,
> but I wonder if it's really worth the effort.

+1

Thanks,
-- Max